Genes Could Get the Jump on Cane Toads

Scientists who have been using the spread of cane toads to examine genetic mechanisms that limit their range believe that slow adaptation to cold weather is delaying the spread of toads into the southern states.

Prof Lin Schwarzkopf’s team at James Cook University compared the genetic processes occurring in cane toads at three invasion fronts in NSW, western Queensland and Western Australia with processes occurring in toads at the centre of their range to determine the factors limiting their expansion. They found different evolutionary processes at all three range limits.

Western Queensland toads show no evidence of genetic adaptation to the environment. At the edge of their range they live in locations that are much like those at the range’s core.

The Western Australian front is steadily advancing through the Kimberleys and has the highest genetic diversity.

The southern toads are moving south very slowly because they have to adapt to cold conditions there. However, Schwarzkopf said it is only a matter of time before they expand their reach, either because the climate warmed or they adapt.

Schwarzkopf says the cane toads have not yet invaded all their potential habitat. She said that future management efforts in the south should target small populations ahead of the front to help stop them adapting to the cold. “In arid, interior portions of the range, toads will move along major rivers and other wet areas, so management should be targeted there.”

Schwarzkopf said the study, published in Molecular Ecology (http://bit.ly/2c4ImFw), has shown that different genetic processes can occur in the same species at different range edges.